Expression of gamma interferon on circulating lymphocytes in viral infections.

Peripheral blood lymphocytes from a total of 111 patients and 40 healthy individuals were studied for gamma interferon (IFN-gamma) expression on their surfaces by indirect immunofluorescence assay and flow cytometry, with a new anti-IFN-gamma monoclonal antibody (IGMB-14) as a specific reagent. Of 64 patients with proven acute viral infections, 59 had a significantly higher percentage of lymphocytes expressing IFN-gamma on their membranes than healthy individuals did. On the other hand, only 3 (8.9%) of 34 patients with proven bacterial infections had an increased percentage of IFN-gamma-expressing lymphocytes. None of the eight patients with other infections and none of the five with systemic lupus erythematosus showed an increased percentage of IFN-gamma-positive lymphocytes. The percentage of IFN-gamma-expressing lymphocytes during a viral infection was found to be related to different stages of the disease. Finally, some applications of this rapid IFN-gamma assay method in viral diseases are discussed.